Primary hyperaldosteronism—usually called primary aldosteronism—is a hormone-related cause of high blood pressure that can be easy to miss. Testing may be worth discussing if your blood pressure is difficult to control, your potassium is low, or an adrenal nodule has appeared on a scan. Normal potassium does not rule it out, and you should not stop or change blood-pressure medicines before testing unless your clinician tells you how.
When to test for primary hyperaldosteronism
In primary aldosteronism, one or both adrenal glands make too much aldosterone. The hormone helps regulate salt and fluid balance; excess can raise blood pressure and increase potassium loss. The condition is also known as Conn’s syndrome, although that older term is often used more narrowly.
Clues that may prompt screening include:
- Blood pressure that remains high despite three medicines, usually including a diuretic, or that needs four or more medicines to control.
- High blood pressure with low potassium, whether the low result occurred on its own or while taking a diuretic.
- High blood pressure and an adrenal nodule found during imaging for another reason.
- High blood pressure with sleep apnoea, a close relative with primary aldosteronism, or a family history of early-onset high blood pressure or stroke at a young age.
Low potassium is a useful clue, but it is not present in most cases. Estimates in clinical literature suggest that only about 10–40% of people with primary aldosteronism have hypokalaemia. A normal potassium result therefore cannot rule the condition out.
Screening recommendations are evolving. Earlier guidance focused on people with specific risk clues; the Endocrine Society’s 2025 guideline suggests screening all people with hypertension, as a conditional recommendation based on low-quality evidence. Local guidance and access to testing differ, so ask your clinician what approach applies to you. If you are also reviewing your general blood-pressure plan, this guide to managing high blood pressure may help with the broader conversation.
What the aldosterone-to-renin ratio can tell you
The initial screen is a blood test measuring aldosterone and renin. Renin is a hormone that normally helps regulate aldosterone. When aldosterone production is inappropriately high, renin is often suppressed; the aldosterone-to-renin ratio (ARR) compares the two. A high ratio can raise suspicion, especially when aldosterone itself is elevated and renin is low.
There is no single cutoff that applies everywhere. Laboratories may measure renin as direct renin concentration or plasma renin activity, use different assays and units, and set their own thresholds. A ratio should be interpreted alongside the separate hormone results, your clinical picture and the laboratory’s reference criteria—not as a diagnosis by itself.
Medicines can shift aldosterone or renin and make the ARR harder to interpret. Diuretics and mineralocorticoid receptor blockers such as spironolactone can affect the result, as can several other common blood-pressure drugs. Low potassium and testing conditions may also matter. Your clinician may decide to repeat the test or adjust the plan to improve accuracy. Do not stop or alter medicines on your own: any change needs clinical advice and a safe plan to keep your blood pressure controlled.
What may happen after an abnormal screen
Depending on the hormone results and the level of suspicion, a clinician may recommend a suppression test to see whether aldosterone falls as expected. Options include saline infusion, oral salt loading, a fludrocortisone suppression test or a captopril challenge. These tests are not automatic for everyone; newer guidance allows some people with a clear, high-probability biochemical pattern to proceed without confirmatory testing. The best next step depends on your results and the pathway used locally.
If primary aldosteronism is likely or confirmed, imaging can look at the adrenal glands. But a nodule on a scan does not prove that it is producing excess aldosterone or identify which gland is responsible. When surgery is being considered, adrenal vein sampling may be used to compare hormone production from each side and guide treatment.
Treatment depends partly on whether excess aldosterone comes mainly from one gland or both. For suitable people with disease on one side, surgery to remove that adrenal gland may be considered. Medicines called mineralocorticoid receptor antagonists—commonly spironolactone or eplerenone—are often used when both glands are involved, surgery is not suitable, or surgery is not wanted. Your care team can discuss expected benefits, possible side effects and follow-up monitoring.
If one of these clues applies to you, bring your blood-pressure readings, recent potassium results, scan reports and a full medication list to your appointment. A clinician can help decide whether screening is appropriate and how to arrange it safely. This article cannot determine whether you have primary aldosteronism; discuss your results and next steps with a qualified health professional.
